Seismic surveys are conducted to map subsurface features. For example, seismic surveys can help locate oil and gas reservoirs. Land based seismic surveys may include hundreds or thousands of individual seismic sensors placed in or on the ground in a grid pattern over an area covering many square kilometers. An explosive charge, seismic vibrator or other suitable source of acoustic energy generates sound waves that propagate through subsurface features. The sound waves are reflected back toward the surface and sensed by the seismic sensors in the grid. Signals from the sensors are collected and used to map the subsurface features in the survey area.